1. Field
The present disclosure relates to a connection system to connect a power supply apparatus to a load apparatus.
2. Description of the Related Art
Electric vehicles (EVs) equipped with rechargeable batteries are in widespread use today.
To charge a battery, power is supplied to the EV from an external power supply apparatus. To discharge the battery, power is supplied from the EV to a load apparatus external to the EV.
A variety of techniques have been disclosed to ensure reliability of power transmission of the EV (namely, charging and discharging of the battery). Japanese Unexamined Patent Application Publication No. 2013-74762 discloses an arrangement in which a fuse to block an excessive current is mounted in a connection plug forming an electric path between a power supply apparatus (or a load apparatus) and an EV.
A fuse, if ideal, has a zero operation time to block an excessive current. In other words, an ideal fuse would be blown at the moment an excessive current flows. The electric path is thus opened, blocking the excessive current.
However, the operation time of an actual fuse to block an excessive current is not zero. The actual fuse is unable to block an excessive current through a duration of time from (i) the moment the excessive current flows to (ii) the moment the fuse is blown (namely, the operation time).
The technique disclosed in Japanese Unexamined Patent Application Publication No. 2013-74762 does not take into account the operation time of the fuse. In the technique disclosed in Japanese Unexamined Patent Application Publication No. 2013-74762, there is a possibility that an excessive current instantaneously flows through the electric path between the EV and the load apparatus when power is supplied to from the EV to the load apparatus.
To protect the electric path, a protection circuit (such as an over-voltage protection relay) may be arranged in the EV. Even with the protection circuit, however, an excessive current may flow instantaneously when a fuse is blown and may weld the protection circuit. If the protection circuit malfunctions as a result of welding, the value of a voltage applied between input terminals of the load apparatus is difficult to accurately measure. Reliability of the power transmission is thus degraded.
The problem created by the welded protection circuit is described in detail below by exemplifying a comparison example to a first embodiment of the disclosure with reference FIG. 15, and FIG. 16.